Patent Literature 1 describes an individual identifying device which detects a finger rubbing sound generated by a user rubbing his/her fingers with a microphone, filters the detected signals to take out ultrasonic signals, performs feature extraction based on the ultrasonic signals, and compares the extracted feature information with prestored feature information to determine whether a coincidence occurs between these pieces of information.
Various information input devices have been proposed which use a bodily motion to control the operation of electrical appliances. Such known information input devices include, for example, those which detect audible sounds generated by a frictional motion of fingers (hereinafter, referred to as “finger snapping”), or detect the acceleration of a user's wrist (e.g., see Patent Literature 2), or detect the shape and motion of a user's palm (e.g., see Patent Literature 3) to input information. Such information input devices operated by using part of a human body are expected as user interfaces which can be intuitively operated without requiring pushes of many buttons.
Regarding technology for watching over individuals, watching systems sensing daily-life sounds have been proposed. For example. Patent Literature 4 describes a monitoring system which includes a sound sensor device installed in living space, processes sound signals with a microcontroller to generate spectrogram simplified in both time and frequency domains, transmits the spectrogram from a home gateway to a monitoring server through a network, and causes the monitoring server to apply filters to the spectrogram, to compute score values for the filters, and to identify the situation of a target on the basis of the score values.